Once upon a time, scraps like carrot tops and potato peels might have gone into the garbage - or, more recently - the compost bin. But now creative cooks have ways to use up all parts of the vegetable in delicious ways.

Lynne Char Bennett's column in the May 12 Chronicle Food & Wine section showed how to do just that with radish leaves. So instead of throwing out those greens when you buy a bunch of radishes, turn them into a delicious pesto.

For more ideas for this and other seasonal ingredients, go to the Food tab on The Chronicle's premium website, www.sfchronicle.com.

Radish Leaf Pesto Crostini

Makes 24 crostini

Radish leaves have a similar, but milder, pepperiness to the radishes themselves. Like radishes, the intensity can vary, so if the leaves are very peppery, use a fruitier olive oil. Use your favorite crostini recipe, or purchased crostini. You can also use this spread as you would any pesto - to enliven a minestrone, toss with roasted potatoes or other vegetables, or garnish a pasta.

4 ounces tender radish tops (from about 2 small-leafed bunches)

1/4 cup extra virgin olive oil

1/4 cup unsalted roasted peanuts

1/4 teaspoon minced garlic

1/4 cup olive oil or canola oil

-- Kosher salt

3/4 cup ricotta cheese

24 crostini

-- Radish slices, to garnish

-- Maldon salt

-- Freshly ground black pepper

Instructions: Pick through the radish leaves; discard any old ones and the tough stems. Rinse the leaves well in several changes of cool water until the water remains clean. (When rinsing, remove the leaves from the dirty water, then change the water in the bowl. Dumping everything into a colander can dump the dirt back onto the leaves.) Rinse and slice the radishes thinly for garnish, if desired.

Quickly blanch the leaves in a pot of well-salted boiling water for 5-10 seconds, then plunge in ice water to stop the cooking and set the color; drain and squeeze dry. You should have about 1/3 cup leaves; coarsely chop and place in a blender.

Add the extra virgin oil, peanuts and garlic to the blender, then process until well chopped. Drizzle in the olive or canola oil, and continue blending, stopping to scrape as needed, until the mixture becomes fairly fine; it's OK if there are small pieces of nuts.

Transfer mixture to a bowl and season with salt to taste. If making ahead, place a piece of plastic wrap directly on the pesto, then cover and refrigerate. The pesto will keep a few days before it oxidizes and the green color fades. Makes about 1/2 cup.

To assemble: Spread about 1 1/2 teaspoons ricotta cheese on each crostini, top with about 1 teaspoon of pesto and garnish with the sliced radishes. Finish with a sprinkle of Maldon salt and grind of pepper.